In a medium saucepan over low heat, melt 3 tablespoons of unsalted butter. Once melted, add 4 cups of mini marshmallows, stirring constantly until smooth and glossy, about 5 minutes.

Remove the saucepan from heat and fold in 6 cups of Fruity Pebbles cereal, ensuring each piece is coated with the marshmallow mixture.

Using a greased rolling pin or taco mold, scoop portions of the mixture onto a parchment-lined baking sheet and shape into taco shells. Cool for about 15 minutes.

In a mixing bowl, beat 8 ounces of softened cream cheese until smooth. Gradually add 1 cup of powdered sugar and 1 teaspoon of vanilla extract, mixing until fluffy.

In a separate bowl, whip 1 cup of heavy whipping cream until stiff peaks form, about 3-5 minutes. Be careful not to over-whip.

Gently fold the whipped cream into the cream cheese mixture until combined. Spoon or pipe the cheesecake filling into each taco shell.

Place the filled tacos in the refrigerator for at least 30 minutes to allow the filling to firm up.